The Comorbidity of PTSD and MDD: Implications for Clinical Practice and Future Research

The high prevalence of post-traumatic stress disorder (PTSD) and major depressive disorder (MDD) comorbidity is well established, with comorbidity rates often between 30 and 50%. However, despite the high prevalence of this comorbidity, very few researchers have explored specific treatments for individuals who present with comorbid PTSD and MDD. Further, there has not been explicit examination of the mechanisms through which MDD influences trauma-focused therapy. As individuals with comorbid PTSD and MDD often present with a more chronic course of impairment and in some instances, a more delayed response to treatment, the need for such research is imperative. It will be proposed that there is merit in targeting depression within the treatment of comorbid PTSD and MDD. Accordingly, in this article we review explanations for the high PTSD and MDD comorbid relationship and highlight variables likely to explain such comorbidity. Theoretical accounts for how depression impedes optimal recovery from PTSD and the associated empirical findings are illustrated. We consequently argue that there is a need to develop and test treatments that target both PTSD and MDD symptoms. Directions for future research are highlighted.